Relief valves



March 28, 1961 C. M. F RYE RELIEF VALVES Filed March 28, 1958 "\/B, ZMM,

United States Patent lice Karma VALVES Colin Michael Frye, St. Andrews, Mitton, near Tewkesbury, England, assiguor to Dowty Mining Equipment Limited, Tewkesbury, England, a British company Filed Mar. 28, 19158, Ser. No. '724,677 y 4 Claims. (Cl. IS7- 5395) This invention relates to relief valves ofthe type hereinafter called the type specified, in which a spring-loaded and guided valve element, usually a ball, partly enters a circular valve seat before engaging it andclosing the valve to ow of lfluid. The spring-loading and the area of the valve seat aperture will determine the uid pressure which must exist under the valve seat in order to lift the valve element to allow ow of the uid past the valve. It is well-known that such a relief valve will usually reseat at a lower pressure than that necessary to open it due to frictional resistance to movement of the valve element and the fact that the element may be slightly misaligned with the seat. In some applications, such for example as in hydraulic pit props, such a relief valve is required to control the collapse of the prop under excessively heavy roof loads and if the difference between the relief valve reseating pressure and the opening pressure is too great the prop will yield to the roof load at an unnecessarily high rate. I haveY already described in Patent No. 2,699,180 a construction of relief Valve ensuring concentricity of the valve element and its seat, which construction is incorporated herein. The present invention, while it incorporates the distinctive features disclosed in my prior patent ofthe above number, differs therefrom in that the laterally shiftableV valve seat annulus is located at the higher pressure side of the bore communicating between a low pressure chamber and a higher pressure chamber in the housing (as the terms low pressure and higher pressure are hereinafter defined), instead of at the low pressure side of such bore, along with the valve seating spring and valve element, whereas in the prior patent all are located at the low pressure side. The rearrangement according to this invention kallows the adjustable valve seat to be positively and accurately centered relative to the guide for the valve element, prior to installation of the latter or subjection of the valve element to hydraulic pressure, as was required by the prior arrangement, and to be secured in that accurately centered position. This affords a simpler construction, simpler alignment procedure, and a reduction in overall diameter as a result of fewer concentric parts.

ln accordance with the present invention, a relief valve of the type specified comprisesv'a hollow housing, a transverse wall in the housing including a port, a spring-loaded valve element guided for axial movement with respect to the port, an annular valve seat arranged to be adjustable laterally within limits in the housing and a clamp member situated at the high-pressure side of the valvek seat and adapted to clamp the annular valve seat against the transverse wall in a laterally adjusted position within the limits. Contrary to the conditions obtaining in my prior patent, the clamping pressure against the transverse wall is oppoite to the spring pressure of the valve element against the seat. By this arrangement accurate centering ofthe valve seat with the guided valve element may be assured before the relief valve is subjected to hydraulic pressure by suitably locating the valve seat against the transverse wall 2,976,883 Patented Mar. 28, 1961 during the clamping down of the clamp member, by the Whiah wreaths "alvsmsmber includes a simular,-

procedure hereinafter explained. Also the location of the clamp member at the high-pressure side of the valve seat allows the relief valve housing to be kept to a comparatively small diameter so that the relief valve may takethe form of a slim capsule which can be conveniently mounted in the ram head of the pit prop. A preferred method of locating the valve seat isk to employ a tting tool comprising a spigot which is an accurate lit in the port and includes an accurately aligned extension which fits accurately into the valve seat aperture.

In a preferred construction of the valve the port in the transverse wall forms a guide in which the valve element slides, the' loading spring being located in the low pressure part ofthe housing and being vadjustable by means of an adjusting screw in the housing. Fluid which has passed the valve may leave the low pressure part of the housing through any suitable passage formed therein.

In order that the invention may be clearly understood one embodiment thereof -as used in a hydraulic pit prop will be described with reference to the accompying drawings, in which:

Figure 1 is a vertical section of the lower end of a hydraulic pit prop showing the valve in cross-section as mounted in position in the ram head, and

Figures 2 and vS'are respectively sectional Velevation and plan of a fitting tool for use in accurately adjusting the relief valve during assembly.

rReferring to 'Figure 1 of the drawings, the klower part only of the pit prop. is shown which comprisesthe cylinder i 1 in which a hollow ram 2 isslidable. AThe lowerend of .able operating mechanism. A relief valve assembly-9, the subject of the present invention, is mounted in a cy- Y lindrical hole 11 in the piston 3. v l

This reliefV valve assembly comprises a housing 12V of external hexagonal shape which includes two bores 13 and *14 extending respectively from ther upper and lower ends ofthe housing 12. The bore 13 is correctly designated a low pressure bore, whereas the bore 14 under certain Working conditions-is subject to higher pressure. For convenience these -bores 13 and.14 may be designated respectively as low pressure and high pressure bores, but

such designations are not to be understood as limitations.

These two bores terminate. centrally lof the housing to form a transverse wall 15 kthrough whichV a small diameter bore orl port 16 is accurately formed. This port 16 forms.

the guideyfor the valve carrier 17 extending through it., The valve -carrier 17 is externallyof circular section to I bear against the sides of the port 16 so as accurately to locate the valve element 1S which is a ball held -interiorly ofthe carrier 17. K'lfwo atsonthe carrier (shown byv spacing in Figure 1) `alIOWapasSage for liquid from the valve seat 11'9, later referred to, into ybore 13. The lower surface of the wall 15 -ismade plane and perpendicular to the axis of housing 12. Against'this plane surface an annular valve seat member 19 is clamped'by'means of a screw-threaded clamp member 21 which engages in the ibore 14. Axially ofthe clamp member 21 a passage22 is formed which opens at its lower end into the pressure space of the pit prop. 'Ihe end of the clampmernber The interior ofthe ram 2 forms a reser-;

nordsee rubber seal 23 which ensures that pressure liquid cannot leak around the valve seat member. The lower end of the clamp member 22 comprises a cylindrical portion 24 which has an accurate t in the bore 11 together with a hex-agen head 25 which engages the lower side of the piston 3 to hold` the relief valve assembly in the piston 3 against the pressure in the working space. The rubber seal 26 around the cylindrical portion 24 prevents leakage of fluid from the pressure space past the relief valve assembly. The relief valve assembly, thevsealing ring 4 and the valve 7 are all retained in position by a sheet metal stamping 27 secured by screws (not shown) to the underside of the piston 3. As far as the relief Valve assembly is concerned it will be appreciated that it .has a tight press tit in the bore 11 andthe pressure applied to its lower end is such as to maintain the whole assembly in position against the reaction ofthe engagement of the hexagon head 25Y against the bottom of the piston 3.

The upper end of thevalve element carrier 17 is formed with a stem 28 about which is located a recessed spring carrier 219 having a lower Y spring-engaging flange 31. The part-spherical upper end of the spring carrier 219 tits accurately into a recess 32 formed in an adjusting nut 33 locatedv in the upper end of bore 13. The compression spring 34 acts between the nut 33 and the flange 31, the force then being transferred through stem 28 to the valve element 1S. Liquid which has passed through the valve seat member 19 may escape from the bore 13 into the rarn through a small passage 35 which may form a restricted orifice acting in the manner substantially as disclosed in prior United States Patent No. 2,699,180.

When the prop is in use it is erected by operation of the pump piston 6 which forces liquid from the ram past valve 7 into the pressure space to lift the prop into engagement with the roof. After the prop has been erected in position and the roof loading increases, the liquid pressure in the pressure space will also increase until the force exerted on the valve element 13 over the area of the circular valve seat is substantially equal to the loading of spring 34. The valve will then open allowing passage of a small amount of liquid such that the prop will slightly contract and lower the pressure in the pressure space. With this lower pressure the force on valve element 18 would not be suicient to hold the valveopen and it will reseat, reseating being assisted partly by the fact that orifice 3S is comparatively small thus causing an increase in pressure in the bore 13. Accurate reseating of the valve element will depend entirely on accurate positioning of the valve seat member 19. If this member is accurately positioned the valve element will contact the seat equally all around the seat and closure will be substantially immediate with the minimum of pressure drop from the pressure at which the valve opens.

Accuracy of reseating was, in my prior patent, obtained by subjecting the installed valve to unseating pressure, whereupon the valve seat, then free to -move axially and laterally, was moved by the existing pressure into engagement with the valve. This accurately related the valve and its seat, and the valve seat was then clamped in such position. According to the present invention, in order to ensure accurate alignment of the valve seat member 19 the fitting tool disclosed in Figures 2 and 3 is used during assembly of the relief valve, and-prior to its installation. This fitting tool comprises a hollow Vhexagonal member 35 in which a spigot 37 is loosely located by means of a bush 38 and -a bar 39u The spigot tits tightly into the bush 3S whilst the -bar 39 extends transversely through holes in the member 36 and bush 38. The spigot 37 is accurately machined at its end to three diameters, the lower diameter 41 which is an accurate tit in the aperture of the annular valve member 19', the diameter 42 which is an accurate sliding t within the bore 16 and the upper diameter 43 which is a tight drive fit within the bore 16.

In assembling the relief valve the housing 12. without the valve 18, spring 34, and retaining nut 33p, but with the clamp member 21 and valve seat 19 loosely in position, is inserted into the hexagonal member 36, and the spigot 37 will then enter through bore 13 into bore 16. The lower diameter 41 will enter the bore in the valve seat 19 whilst the diameter 42 will enter the bore 16. Thus, the valve seat member is accurately located relatively to the bore 16. The hexagonal member 36 engages the hexagonal housing 12 against their relative rotation, and using the bar 39 as a lever the clamp member 21 may be tightened in position by use of a Spanner on the hexagon head 25. The seat member 19 is then accurately clamped in position and the valve element (the portion 17 whereof accurately tits the bore 16), the loading spring 34 and the retaining nut 33 may be screwed into the bore 13 when the fitting tool has been removed. The valve and its seat are now accurately related, but to adjust the operating pressure of the relief valve assembly, prior to its installation in the ram head, high pressure Iliquid is supplied to the lower end ofpassageV 22 which includes a screwthreaded. portion 44 for this purpose. The nut 33 is rotated LntilV the correct `opening pressure is obtained. The nut is located in position simply by burring the screw threads in bore 13 at the outer end, or in any other suitable manner, to prevent the nut 33 from turning.

ltwill be seen that arranging the clamp memberl 21 and valve seat 19` at the high pressure end of the valve housing 12, whilst the valve1-7, l and its spring 34 are arranged at the low pressure end, contrary to the arrangement -in my priorpatent, wherein all such parts were at the low pressure end, allows the housing to be of slimV proportions. Furthermore the valve seat 19 canl be accurately centered without having to install the valve or to subject it- .to hydraulic pressure, and its closing pressure can be accurately set before its installation.

' l claim as my invention:

l. A relief valve comprising a housing having opposite ends respectively with coaxial highV pressure and low pressure bores therein, -a transverse wall intermediate said bores having afport coaxial with said bores and communicating with each thereof, means including guide means slidably and closely received in said port for axial movement therein, passage means-formed between said guide means and said port to afford communication between said bores, a valve element closely carried within said guide means and guided bythe latter for accurate axial movement in said port, spring means in the low pressure bore urging saidl guided valve element in the direction toward the high-pressure bore, an annular valve seat positioned against the high-pressure side of said wall and engageable by the valve element extending through said port, said valve seat having a planar `face normal to the axes of the bores and the transverse wall having a complemental planar face at its high pressure side whereon the valve seat is transversely shiftabie for adjustment in different transverse directions for precise axial alignment of said valve seat with said guided valve element and thereby accurate seating of said valve element7 and a clamp member received and guided for axial movement within the high-pressurey bore into engagement with said annular valve seat and thereby to clamp and hold the latter against the wall in the adjusted axially aligned position of such valve seat.

2. The relief valve dened in claim l, wherein the clamp member comprises a plug inserted in the valve housing bore at the high-pressure side and having a passage cxtending lengthwise through it for passage of fluid from outside the rhousing to the high-pressure side of the valve and valve seat.

3. The relief valve defined in claim 2, wherein the clamp member has an enlarged end portion which extends from the high-pressure end of the housing and comprises an annular fitting element of larger diameter than the housing and sealed to tit fluid-tightly in a mounting bore between the `ends of which liquid pressure is to be relieved by said'valve means.

s 6 4. The relief valve dened in claim 3, yand an annular References Cited in the le of this patent seal element carried by the end of the clamp member engaging the valve seat, and nterposed therebetween, there- UNITED STATES PATENTS by to afford a seal against ow of high-pressure liquid 1,293,604 Woolever Feb. 4, 1919 from Said passage and through the contact between said 5 1,919,973 Berkeley July 25, 1933 clamp member and valve seat. 2,252,924 Hale Aug. 19, 1941 

